All-Fiber Near-Field Optical Tweezer: Reducing Thermal Disturbance

Abstract

Trapping nanoscale particles in a stable and non-destructive way is of great importance to life sciences. Near-field optical tweezers are a common way to trap nanoparticles. Here we propose and demonstrate an all-fiber near-field optical tweezer for trapping nanoparticles using a laser beam that has been totally reflected three times on a fiber tip with a double frustum structure. The light totally internally reflects on the optical fiber end-face and generates an evanescent field that traps the nanoparticles in water. Simulated results show that the evanescent field with high gradient distribution generating on the optical fiber end face leads to an insignificant temperature rise (0.0765 K). The experimental results demonstrate that all-fiber near-field optical tweezer allows us to trap fluorescent particles as small as 100 nanometers in diameter. The max temperature rise is 0.091 K. Compared with the plasmonic optical tweezers, the all-fiber optical tweezer reduces the thermal effect. The proposed all-fiber near-field optical tweezer plays an essential role in nanoscale optical trapping.